select * from

(

select id,max(case when cd = 'A' then 1 else 0 end) + max(case when cd = 'B' then 2 else 0 end) + max(case when cd = 'C' then 4 else 0 end) status from a

--where cd in ('A','B','C')

group by id

) dta

where

1=1

--and status = 3 -- a,b but not c

--and status = 5--does have a,c but not b

--and status = 6--does have b,c but not a

--and status = 7 --all 3

--and status = 0 --none of them

--and status = 1 -- just A

--and status = 2 -- just b

and status = 4 -- just C

Replace Id with CustomerId and cd with ProductCode. You can generalize the code the way you want..You can use analytic function instead of group by as well.